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►Managing Mercury Mania

Jerald O. Thaler, P.E.Fishbeck, Thompson, Carr & Huber, Inc.

Michigan Water Environment AssociationAnnual IPP SeminarSeptember 25, 2008

“Mercury 101”

►The Wake-up Call

• In the 1950s and 1960s, Japan experienced an epidemic of psychotic disease and deformed/brain-damaged births

– Traced to mercury poisoning from eating fish in Minamata Bay

– Tons of mercury chloride was discharged by Chisso Corporation between 1931 and 1968

– Aquatic organisms convert inorganic mercury to highly toxic methylmercury

– Methylmercury bioaccumulates up the food chain (~106x for trophic level 5) Bioaccumulation

►Regulatory Focus

• Michigan has strict, long-standing controlson mercury in wastewater discharges

• Only recently has focus increased on air emissions, where the impact is greater

Mercury Sources to Lake Michigan(adapted from Frequently Asked Questions About

Atmospheric Deposition, USEPA, September 2001)

Tributaries (20%)

Atmospheric Deposition

(80%)

►Discharge Standards

• Rule 57 provides protection against toxicity

• Wildlife protection controls at 0.0013 μg/L, or 1.3 nanograms per liter (ng/L)

• No mixing zone credit for BioaccumulativeChemicals of Concern

CriterionMicrograms per liter

(μg/L)

Acute Toxicity 2.8

Chronic Toxicity 0.77

Human Health 0.0018

Wildlife 0.0013

►Effluent Monitoring

• Method 245.1– Composite sample– Normal handling– Quantification inconclusive

for compliance testing– $40-$50 each

(from Sample Collection for Ultra-Trace Concentrations of Mercury, Florida Department of Environmental Protection,

ftp://ftp.dep.state.fl.us/pub/labs/assessment/ppt/utmsamp.ppt)

• Method 1631– Grab sample– “Clean Hands/Dirty Hands”– Quantification acceptable

for compliance testing– $90 each for 3 samples

(duplicates plus field blank)

►NPDES Permit

• Limits generally set at Level Currently Achievable (LCA) under multiple discharger variance

– Initially 30 ng/L– Recently lowered to 10 ng/L– Soon to change to user-specific LCA

• Applied as 12-month moving average • Effluent monitoring using Method 1631• Mercury Minimization Program required

►Mercury Minimization Program

• Goal to achieve effluent of 1.3 ng/L • Formal plan approvable by MDEQ• Annual status report• Required elements

– Monitoring of influent, effluent, and biosolids– Source identification– Source reduction

• Recommended elements– Public education

Minimization Tips and Techniques

►Avoid the Regulatory Trap

• Mercury in permit if potential effluent quality (PEQ) exceeds 1.3 ng/L

• Per Rule 1211, PEQ is statistical tool to relate quality/quantity of monitoring data

where factor set by number of samples (N):

► PEQ = CMAX * Factor

N Factor

1 6.2

2 3.8

3 3.0

4 2.6

5 2.3

10 1.7

50 1.0

►Avoid the Regulatory Trap

• Permit application generally requires minimum of four effluent samples

• Sometimes more samples may be better

– If 4 samples with CMAX of 0.7 ng/L, PEQ>1.3 ng/L and permit will include mercury

PEQ = 0.7*2.6 = 1.8 ng/L

– If 10 samples with CMAX of 0.7 ng/L, PEQ<1.3 ng/L and permit may not include mercury

PEQ = 0.7*1.7 = 1.2 ng/L

► Flexible Sewer Use Ordinance

• Traditional command-and-control approach: “No discharge of detectable mercury.”

• May not be feasible for some commercial users

– Technical limitations– Economic factors

• Strict enforcement may be counterproductive to local economy

►Flexible Sewer Use Ordinance

• Alternative case-by-case approach: “No discharge of detectable mercury, except as specifically approved.”

• Conditions of approval– Periodic self-monitoring

– Minimization program (procedures, training, source identification/reduction, treatment, etc.)

– All reasonable and cost-effective actions

• Promotes flexibility and cooperation

►Meaningful Monitoring

• Evaluate monitoring data via mass balance to fully assess overall system

• Example:

Identified Sources 0.05 MGD

700 ng/L Hg0.107 lb/yr Hg

Domestic/Background 1.26 MGD

50 ng/L Hg0.192 lb/yr Hg

Unidentified Sources Average Removal

1.474 lb/yr HgBy difference… 98%

2.2 mg/kg Hg1.742 lb/yr Hg

WWTP Influent

1.773 lb/yr Hg

Biosolids (6.5%)

396 T/yr

1.31 MGD 445 ng/L Hg

0.031 lb/yr Hg 7.9 ng/L Hg

1.30 MGD WWTP Effluent

Current Average

►Meaningful Monitoring

• Apply mass balance results to prioritize minimization efforts

Identified Sources 0.050 MGD

200 ng/L Hg 0.030 lb/yr Hg

Domestic/Background 1.25 MGD

50 ng/L Hg 0.190 lb/yr Hg

Unidentified Sources Average Removal

0.073 lb/yr HgBy difference… 98%

0.3 mg/kg Hg 0.255 lb/yr Hg

WWTP Influent

0.250 lb/yr Hg

Biosolids (6.5%)

396 T/yr

1.31 MGD 63 ng/L Hg

0.005 lb/yr Hg 1.3 ng/L Hg

1.3 MGDWWTP Effluent

Goal

-0.077 lb/yr

-1.401 lb/yr

►Productive Source Studies

• Common sources– Domestic sewage (25-50 ng/L)– Dental offices

• Other observed sources– Hospitals and medical clinics– State prisons– Car washes– Rainwater (~10 ng/L) and snowmelt

• Use sampling of collection system to identify significant sources and maintain neutrality

►Productive Source Studies

• Scattered sampling can be inconclusive due to high variability of mercury

• Most efficient is moving upstream via “primary/secondary” scheme

S-2

S-1

P-1 P-2

S-1' S-2'

Source

WWTP

►Deal With the Dentist

• The most common controllable source of mercury

• Mercury inherent to dentistry due to mercury-silver amalgams

• Special challenge for smaller communities with multiple dentists

• Typical mercury generated per office0.57 lb/yr Amalgam removal (97%)0.02 lb/yr Amalgam placement (3%)0.59 lb/yr Total

• Removals for typical capture processes ~ 68% Chair-side traps ~ 40% Vacuum filters 81% Overall

• Typical sewer discharge per office0.59 * (1-.81) = 0.1 lb/year

(ENVIRON International Corp., Evaluation of Mercury in Dental Facility Wastewater, Ver. 3, American Dental Association, Nov. 2002)

►Deal With the Dentist

• Potential impact on treatment plant Assuming 2.5 million gal/day flow

No.

Dentists

Dental Mercury

(lb/yr)

Influent

Impact (ng/L)

Domestic Background

(ng/L)

Net

Influent

(ng/L)

WWTP

Removal

Net

Effluent

(ng/L)

0 +0.0 +0 50 1.0

1 +0.1 +13 63 1.3

2 +0.2 +26 ~50 76 ~98% 1.5

4 +0.4 +53 103 2.1

8 +0.8 +105 155 3.1

►Deal With the Dentist

• Amalgam Separator– >95% mercury removal for wet

vacuum systems– Not overly complex or expensive– Can produce significant

improvement at treatment plant

“…[Amalgam separator] systems work well, and we now feel comfortable including them

in our best management practice recommendations."

Dr. Mark J. Feldman, PresidentAmerican Dental Association

October 11, 2007

►Deal With the Dentist

• Potential impact on treatment plant Again assuming 2.5 million gal/day flow

No. Dentists

Amalgam Separator Removal

Dental Mercury (lb/yr)

Influent

Impact (ng/L)

Domestic Background

(ng/L)

Net Influent (ng/L)

WWTP Removal

Net Effluent

(ng/L)

0 +0.000 +0 50 1.0

1 +0.005 +0.7 50.7 1.01

2 95% +0.010 +1.3 ~50 51.3 ~98% 1.03

4 +0.020 +2.6 52.6 1.05

8 +0.040 +5.3 55.3 1.11

►Deal With the Dentist

• Proposed Legislation – SB-1310/HB-6307 mandate amalgam separators by

December 31, 2013– Michigan Board of Dentistry to promulgate associated

best management practices– However, prevents local authorities from pursuing

further source reduction where warranted

►Deal With the Dentist

“This… supersedes any local ordinance… that imposes… additional standards on dentists… including… a permit that limits the discharge of mercury… greater than that capable of being achieved by full compliance with this section.”

►Perspective

• Justifiable concern over mercury in waterways– Air emissions need same, or greater, scrutiny as

wastewater discharges

• Tips and techniques from experience– Avoid the regulatory trap– Flexible sewer use ordinance– Meaningful monitoring– Productive source studies– Deal with the dentist

• Resist legislation that, while well-intended, pre-empts local authority/control

For additional information:

Jerald O. Thaler, P.E.Fishbeck, Thompson, Carr & Huber, Inc.

39255 Country Club Drive, Suite B-25Farmington Hills, MI 48331

jothaler@ftch.com248-324-2090

►Questions and Discussion